After hours and hours in this insane bug.. To make it work I had to open a VPN connection to a China server. Instead of install PlexVPN I setted up a VPN directly on the phone configuration using server from http://www.vpngate.net/en/ Address: vpn959922015.opengw.net User: vpn Pass: vpn Pre-shared key: vpn

VPN Configuration

With the connections through VPN, I can enable "Install via USB".
Please, solve this bug soon.

100% worked solution described in posts #178, #179, #180, #181:
:
1) Just install "Transocks VPN" from Google Play Store
2) Click on the circle at the top of the screen with Chinese text.
3) Wait for connect to server
4) Go to Developer Settings
5) Click "Install via USB"
6) Enjoy!